Neutron Stress Measurements with a Position Sensitive Detector.

Abstract : The feasibility of measuring residual and applied stresses with neutrons employing a position sensitive detector (PSD) is demonstrated. Measurements with both a small beam, to probe internal regions, and a large beam, for bulk sampling have been made. With such a detector collection of data is rapid compared to ordinary neutron collection methods. This detector allows more detailed sampling, smaller probe regions and possibly even study of time-dependent processes. The spectrometer geometry is shown in Fig. 1a. The detector consists of a three-counter array of linear PSD's spanning a usable angular range of 25 degrees 2 theta at a distance of 1220 mm from the sample position. The detectors are stacked in a vertical plane which is normal to the horizontal diffraction plane. The front of the detector housing has an oscillating radial collimator which greatly reduces background and off-axis scattering. The data is rebinned into 0.1 degrees 2 theta increments from the basic channel width of approximately 0.03 degrees and the intensity of the three detectors is added. From these experiments we have shown that the PSD in use at the University of Missouri Research Reactor Facility is an important tool for the application of neutron scattering to engineering materials, in addition to its use in more traditional neutron scattering experiments. This is because of the significant savings in data collection time and the increased range of feasible experiments. The resolution and behavior of this instrument has been demonstrated to be on a par with standard detectors.